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Hagerty Employee

Piston Slap: Suboptimal flare in the Optispark?

Keith writes:


My 1996 Corvette convertible got extremely hot on me while I was idling in a parking lot. While attempting to get it home, the lights on the dash started going off, and then she shut down altogether. I towed it home and checked the oil. It looks fine. The engine turns over but will not fire. I sprayed a shot of ether down its throat but it still wouldn't fire. Do these engines have an automatic shut off? I disconnected the battery for over an hour, reconnected it, and it still won't fire. Any suggestions? Thanking you in advance.


Sajeev answers:


I suspect you have a no-spark condition after the engine overheated, and those familiar with the second-generation Chevrolet LT1 (and LT4) know exactly where I'm going.


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Negative Ghostrider! 
We who freak over the second gen small block, seasoned optispark apologists all, know to withhold judgement until we have ruled out the possibility of an ignition coil module failure. The second rule of optispark club is to never ever replace a genuine OEM optical sensor in the unit (made by Mitsubishi) with any aftermarket unit. If it is the opti, pick a cap and rotor within your budget, and while you are in there replace the front timing seals, which will leak and allow oil into your opti

Community Manager

Oh, this is very good information, thank you so much for contributing!  Will the ignition coil module failure show up as a fault code in the engine computer? 


ICM codes on a 96 (obd2) should be P1350-P1370


Sajeev may be right about the Opti, but as a fellow C4 owner, I strongly suggest that you also address the source of your problem as well.  Namely, cool down that engine bay.  Essentially, what you have is a plastic easy-bake oven holding in the heat from a big V-8.  There is very little air getting in under the hood, and precious little heat escaping, under a plastic hood that holds all that heat in place.  Add to that, that the idiots at Bowling Green set the engine to run too hot to begin with, so they could meet EPA standards, and your engine is cooking itself to death.  There are lots of ways to cool down the engine bay, from a lower temp thermostat, to opening up the air intake under the nose with a Big Mouth air dam or vented spoiler, and letting heat escape through vented side-fenders and a vented hood.  I have done all of the above on mine, and it makes a huge difference.  I have the twin-turbo aftermarket hood on mine, and if you stand near the windshield, near where the hood heat vents are, the amount of hot air rolling out of the engine bay will really astound you.  I have a vented front spoiler that really opens up the cool air intake, and all that extra air flow really pushes the heat out.  You could also install a 3-row aluminum radiator, a high-volume water pump, an oil cooler and a tranny cooler as well.  Heat is the enemy of your engine.